Stepped punch for forming holes in molded wood strand parts

ABSTRACT

A mold for forming wood flakes into a molded wood flake part including a top mold die and a bottom mold die. The top mold die includes a punch for forming a hole in the part, and the bottom mold die includes a punch receiving aperture. The punch includes a tapered upper portion and a cylindrical lower portion for forming the hole in molded parts of varying thicknesses. The punch includes a tapered upper section defining an upper opening of a first radius in a top surface of the molded part and a cylindrical lower section defining an opening of a second radius in a bottom surface of the molded part. The cylindrical lower portion is sufficiently long that the bottom opening in the hole in each part formed will have the same second radius.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to wood flake molding.

B. Background of the Art

Wood flake molding, also referred to as wood strand molding, is atechnique invented by wood scientists at Michigan TechnologicalUniversity during the latter part of the 1970s for moldingthree-dimensionally configured objects out of binder coated wood flakeshaving an average length of about 1¼ to about 6 inches, preferably about2 to about 3 inches; an average thickness of about 0.005 to about 0.075inches, preferably about 0.015 to about 0.030 inches; and an averagewidth of 3 inches or less, most typically 0.25 to 1.0 inches, and nevergreater than the average length of the flakes. These flakes aresometimes referred to in the art as “wood strands.” This technology isnot to be confused with oriented strand board technology (see e.g., U.S.Pat. No. 3,164,511 to Elmendorf) wherein binder coated flakes or strandsof wood are pressed into planar objects. In wood flake or wood strandmolding, the flakes are molded into three-dimensional, i.e., non-planar,configurations.

In wood flake molding, flakes of wood having the dimensions outlinedabove are coated with MDI or similar binder and deposited onto a metaltray having one open side, in a loosely felted mat, to a thickness eightor nine times the desired thickness of the final part. The looselyfelted mat is then covered with another metal tray, and the coveredmetal tray is used to carry the mat to a mold. (The terms “mold” and“die”, as well as “mold die”, are sometimes used interchangeably herein,reflecting the fact that “dies” are usually associated with stamping,and “molds” are associated with plastic molding, and molding of woodstrands does not tit into either category.) The top metal tray isremoved, and the bottom metal tray is then slid out from underneath themat, to leave the loosely felted mat in position on the bottom half ofthe mold. The top half of the mold is then used to press the mat intothe bottom half of the mold at a pressure of approximately 600 psi, andat an elevated temperature, to “set” (polymerize) the MDI binder, and tocompress and adhere the compressed wood flakes into a finalthree-dimensional molded part. The excess perimeter of the looselyfelted mat, that is, the portion extending beyond the mold cavityperimeter, is pinched off where the part defining the perimeter of theupper mold engages the part defining the perimeter of the lower moldcavity. This is sometimes referred to as the pinch trim edge.

U.S. Pat. Nos. 4,440,708 and 4,469,216 disclose this technology. Thedrawings in U.S. Pat. No. 4,469,216 best illustrate the manner in whichthe wood flakes are deposited to form a loosely felted mat, though themetal trays are not shown. By loosely felted, it is meant that the woodflakes are simply lying one on top of the other in overlapping andinterleaving fashion, without being bound together in any way. Thebinder coating is quite dry to the touch, such that there is nostickiness or adherence which hold them together in the loosely feltedmat. The drawings of U.S. Pat. No. 4,440,708 best illustrate the mannerin which a loosely felted mat is compressed by the mold halves into athree-dimensionally configured article (see FIGS. 2-7, for example).

This is a different molding process as compared to a molding process onetypically thinks of, in which some type of molten, semi-molten or otherliquid material flows into and around mold parts. Wood flakes are notmolten, are not contained in any type of molten or liquid carrier, anddo not “flow” in any ordinary sense of the word. Hence, those ofordinary skill in the art do not equate wood flake or wood strandmolding with conventional molding techniques.

Some parts are designed with holes in them, for example, for receivingso called “T” nuts. T nuts comprise an annular flange with one or morebarbs projecting therefrom for anchoring the T nut in the surface of thepart, and with an internally threaded sleeve extending perpendicularlyfrom the annular flange. Thus, the hole in the part must extendperpendicularly back from the surface of the part. Such holes may alsobe required for other purposes.

While such holes can be drilled into a molded wood strand part after itis molded, it would be preferable to mold the holes into the part aspart of the molding process. To do so, the mold cavity is provided witha punch projecting from one surface thereof, and a hole defining punchreceiving insert in the opposite mold cavity surface, such that as theupper and lower mold halves, or platens, are closed, the punch pushesthrough the loosely felted mat, pushing wood flakes aside or bendingthem in the direction of the punch, such that as the binder cures, ahole is formed around the punch.

Heretofore, the holes have been with a punch having a tapered outersurface that pushes past and through the wood strands in the felted,mat. The punch is tapered to facilitate its removal from the moldedpart. However, due to the nature of wood strand molding, the finalmolded part can vary ill thickness. The mats can be compressed tovarying thicknesses by the mold die, due to unavoidable inconsistenciesfrom mat to mat, springs back of the mat, overcompression, or file like.Therefore, the dimensions of an opening on one side of a molded holeformed by a tapered punch can vary with variations in the finalthickness of the part, depending on the distance the tapered punchextends through the molded part. Therefore, while the openings on oneside of a hole may have the same radius for all molded parts using thatpunch, the openings on the other side of the hole will have varyingradii, depending on the thickness of the molded part.

SUMMARY OF THE INVENTION

In the wood flake molding process and apparatus of the presentinvention, the punch for forming holes in the part includes a taperedupper portion to facilitate mold release, but a cylindrical lowerportion for forming a hole of consistent dimensions in parts of varyingthicknesses. The tapered upper portion is configured to extendsufficiently far into the molded wood flake part to facilitatewithdrawal of the punch from the hole formed therein. The cylindricallower portion is sufficiently long that regardless of variations in partthickness, the bottom opening in the hole in each part formed will havethe same radius, defined by the cylindrical lower portion.

The mold is efficient in use, economical to manufacture, capable of along life, and particularly adapted for the proposed use.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational cross sectional view of the spaced upperand lower mold halves with a loosely felted mat of wood flakespositioned there between.

FIG. 2 is the same view of FIG. 1 with the mold closed, whereby the woodflakes are consolidated, compressed, and cured under beat and pressureto form a molded wood flake part.

FIG. 3 is a side elevational view of a punch and a punch receivingaperture in a punch receiving insert used to accept the punch duringmolding of the molded wood flake part.

FIG. 4 is a partial, cross-sectional view of the molded wood flake part.

FIG. 5 is a partial side cross-sectional view of a punch and punch baseused to form holes in the molded wood flake part with the wood flakesconsolidated, compressed and cured into the molded wood flake part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of description herein, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the invention as orientated in FIG. 1. However,it is to be understood that the invention may assume various alternativeorientations, except where expressly specified to the contrary. It isalso to be understood that the specific devices and processesillustrated in the attached drawings, and described in the followingspecification are simply exemplary embodiments of the inventive conceptsdefined in the appended claims. Hence, specific dimensions and otherphysical characteristics relating to the embodiments disclosed hereinare not to be considered as limiting, unless the claims expressly stateotherwise.

The reference number 10 (FIG. 1) generally designates a mold of thepresent invention. The mold 10 is used in a method of forming woodflakes 12 into a molded wood flake part 14 (FIG. 2). The mold 10includes a top mold die 16 and a bottom mold die 18. The top mold die 16includes a surface 20 and a punch 22 extending from the surface 20 forforming a hole 24 (see FIG. 4) in the part 14, and the bottom mold die18 includes a surface 26 having a punch receiving aperture 28. Thesurface 20 of the top mold die 16 and the surface 26 of the bottom molddie 18 define a cavity 30 therebetween. The punch 22 projects into thecavity 30 from the surface 26 of the top mold die 16, and includes atapered upper portion 32 and a cylindrical lower portion 34 for formingthe hole 24 in molded wood flake parts 14 of varying thicknesses. Thetapered upper portion 32 is configured to extend sufficiently far intomolded wood flake part 14 to facilitate withdrawal of the punch 22 fromthe hole 24 formed therein. The cylindrical lower portion 34 issufficiently long that regardless of variations in part thickness, thebottom opening 46 in each part 14 formed will have the same secondradius 48, defined by the cylindrical lower portion 34.

In the illustrated example, the molded wood flake part 14 is made bypositioning a loosely felted mat 52 of wood flakes 12 on the bottom molddie 18 (FIG. 1). The top mold die 16 and the bottom mold, die 18 arethen brought together (FIG. 2) and heat and pressure are applied to thefelted mat 52. The felted mat 52 is thereby compressed and cured intothe molded wood flake part 14 having the hole 24 formed therein by thepunch 22 passing through the mat 52 and forcing the wood flakes 12 downinto the punch receiving aperture 28. Although only one punch 22 isshown in the illustrated example, a plurality of punches could be usedto form a plurality of holes in the molded wood flake part 14.

The illustrated mold 10 (FIG. 3) includes a base 54, the tapered upperportion 32 and the lower cylindrical portion 34. The base 54 is insertedinto a receiving socket 56 (see FIG. 1) in the top mold die 16, as, forexample, by threading into the socket 56. The base 54 includes a baseface 57 that is generally aligned with the surface 20 of the top molddie 16. The tapered upper portion 32 has a generally frusto-conicalconfiguration with a larger diameter of the tapered upper portion 32connected to the base 54. The cylindrical lower portion 34 of the punch22 extends from the tapered upper portion 32. Preferably, thecylindrical lower portion 34 has about the same vertical length as thetapered upper portion 32. The cylindrical lower portion 34 of the punch22 is designed to extend downwardly into the punch receiving aperture 28located in the bottom mold die 18.

In the illustrated example, the punch receiving aperture 28 is locatedin a punch receiving insert 58 (FIG. 3) positioned in the bottom molddie 18. The punch receiving insert 58 includes a body 60 which isinserted into and secured in a socket 62 in bottom mold die 18 in thesame manner that the base 54 of the punch 22 is inserted into andsecured in the receiving socket 56 in top mold die 16. In addition tothe punch receiving aperture 28, the punch receiving insert 58 includesa top face 64 which is intended to align with the surface 26 of thebottom mold die 18 and the base face 57 of the base 54 of the punch 22.As can be seen in FIG. 3, the punch receiving aperture 28 in the punchreceiving insert 58 is tapered downward with horizontal dimensionssomewhat larger than the punch 22. This is so the punch receivingaperture 28 will accommodate wood flakes 12 which are pushed downwardlyinto the punch receiving aperture 28 by the punch 22 as it passesthrough loosely the felted mat 52. These wood flakes 12 that are pusheddown into the punch receiving aperture 28 are referred to as a plug.

The molded wood flake parts 14 made from the mold 10 include the hole 24(see FIG. 4) that has a tapered upper section 36 defining an upperopening 38 of a first radius 40 in a top surface 42 of the molded woodflake part 14 and a cylindrical lower section 44 defining a bottomopening 46 of a second radius 48 in a bottom surface 50 of the moldedwood flake part 14. The shape of the hole 24 formed in the molded woodflake part 14 by the punch 22 is quite different, depending on whichside of the molded wood flake part 14 it is viewed from. When viewedvertically from above, the view corresponds to an upper opening 38defined by the tapered upper section 36 of the hole 24 and the taperedupper portion 32 of the punch 22. In contrast, if the hole 24 is viewedfrom the other side of the molded wood flake part 14, one sees a bottomopening 46 defined by the cylindrical lower section 44 of the hole 24and the cylindrical lower portion 34 of the punch 22. However, the shapeand size of the upper opening 38 and the shape of the bottom opening 46will be the same for every molded wood flake part 14 produced regardlessof the thickness of the molded wood flake part 14. The only differencebetween the holes 24 in several molded wood flake parts 14 of varyingthicknesses would be that the cylindrical lower section 44 of the holeswill have varying lengths. The resulting hole 24 provides a uniformappearance from the surface of the molded wood flake part andfacilitates the insertion of a T nut (not shown) from either surface,with its mounting flange and associated bar resting on a surface of themolded wood flake part which has been formed, and with its threadedsleeve projecting inwardly into the hole 24. The width of the hole 24 issufficiently great throughout its length that it will accommodate asleeve of a T nut or other item to be inserted into the hole 24, withoutinterference.

As seen in FIG. 5, the top surface 42 of the molded wood flake part 14is adjacent the surface 20 of the top mold die 16 and the bottom surface50 of the molded wood flake part 14 is adjacent the surface 26 of thebottom mold die 18 after the wood flakes 12 have been consolidated,compressed and cured into the molded wood flake part 14. The molded woodflake parts 14 made in this manner will preferably have a nominalthickness 100. However, the felted mats 52 will be compressed to varyingthicknesses by the mold 10, due to unavoidable inconsistencies from mat52 to mat 52, spring back of the mat 52, overcompression, or the like.Therefore, the bottom surface 50 of the molded wood flake part 14 willbe located within a zone of variation in part thickness 102. The zone ofvariation in part thickness 102 is the area in which the bottom surface50 of the molded wood flake part 14 could be located, depending on thethickness of the molded wood flake part 14, compared to a stationaryposition for the top surface 42 of the molded wood flake part 14.

In order to provide a uniform appearance of the hole 24 from the topsurface 42 and the bottom surface 50 of the molded wood flake part 14,the punch 22 is configured such that the hole 24 will have the upperopening 38 when viewed from above and the lower opening 46 when viewedfrom below. Therefore, the tapered upper portion 32 of the punch 22 willalways be located above within the nominal thickness 100 of the moldedwood flake part 14, but above the zone of variation in part thickness102. Moreover, the cylindrical lower portion 34 of the punch 22 willalways have an upper end 200 within the nominal thickness 100 of themolded wood flake part 14 but at or above the top limit of the zone ofvariation in part thickness 102 and a lower end 202 below the lowerlimit of the zone of variation in part thickness 102, and extendingbeyond the surface of bottom mold die 18, into aperture 28 in punchreceiving insert 58. Therefore, every hole 24 made in the molded woodflake part 14 will have the upper opening 38 when viewed from above andthe lower opening 46 when viewed from below, as described above. Asstated above, the tapered upper portion 32 is configured to extendsufficiently far into the molded part 14 to facilitate withdrawal of thepunch 22 from the hole 24 formed therein. The tapered upper section 32facilitates withdrawal of the punch 22 because of the reduction offriction between the punch 22 of the hole 24, as compared to thefriction involved with removing a cylindrical punch from a circularhole. The tapered upper section 32 therefore should extend from thesurface 20 of the top mold die 16 to a location slightly above the zoneof variation in part thickness 102. For example, if the desired lengthof the hole 24 is ½″, the tapered upper portion 32 of the punch 22 couldhave a length of ⅜″ and the cylindrical lower portion 34 of the punch 22could have a length of ⅜″ creating a hole 24 with a tapered uppersection 36 having a length of ⅜′ and a cylindrical lower section 44having a length of ⅛″, since the remaining ¼″ of the punch projects intoaperture 28 in punch receiving insert 58.

The wood flakes 12 used in creating the molded wood flake part 14 can beprepared from various species of suitable hardwoods and softwoods usedin the manufacture of particleboard. Representative examples of suitablewoods include aspen, maple, oak, elm, balsam fir, pine, cedar, spruce,locust, beech, birch and mixtures thereof. Aspen is preferred.

Suitable wood flakes 12 can be prepared by various conventionaltechniques. Pulpwood grade logs, or so called round Wood, are convertedinto wood flakes 12 in one operation with a conventional roundwoodflaker. Logging residue or the total, tree is first cut into fingerlingsin the order of 2-6 inches long with a conventional device, such as thehelical comminuting shear disclosed in U.S. Pat. No. 4,053,004, and thefingerlings are flaked in a conventional ring-type flaker. Roundwoodwood flakes 12 generally are higher quality and produce stronger partsbecause the lengths and thickness can be more accurately controlled.Also, roundwood wood flakes 12 tend to be somewhat flatter, whichfacilitates more efficient blending and the logs can be debarked priorto flaking which reduces the amount of less desirable fines producedduring flaking and handling. Acceptable wood flakes 12 can be preparedby ring flaking fingerlings and this technique is more readily adaptableto accept wood in poorer form, thereby permitting more completeutilization of certain types of residue and surplus woods.

Irrespective of the particular technique employed for preparing the woodflakes 12, the size distribution of the wood flakes 12 is quiteimportant, particularly the length and thickness. The wood flakes shouldhave an average length of about 1¼ inch to about 6 inches and an averagethickness of about 0.005 to about 0.075 inches. The average length ofthe wood flakes is preferably about 2 to about 3 inches. In any givenbatch, some of the wood flakes 12 can be shorter than 1¼ inch, and somecan be longer than 6 inches, so long as the overall average length iswithin the above range. The same is true for the thickness.

The presence of major quantities of wood flakes 12 having a lengthshorter than about 1¼ inch tends to cause the felted mat 52 to pullapart during the molding step. The presence of some fines in the feltedmat 52 produces a smoother surface and, thus, may be desirable for someapplications so long as the majority of the wood flakes, preferably atleast 75%, is longer than 1⅛ inch and the overall average length is atleast 1¼ inch.

Substantial quantities of wood flakes 12 having a thickness of less thanabout 0.005 inches should be avoided, because excessive amounts ofbinder are required to obtain adequate bonding. On the other hand, woodflakes 12 having a thickness greater than about 0.075 inch arerelatively stiff and tend to overlie each other at some incline whenformed into the felted mat 52. Consequently, excessively high moldpressures are required to compress the wood flakes 12 into the desiredintimate contact with each other. For wood flakes 12 having a thicknessfalling within the above range, thinner ones produce a smoother surfacewhile thick ones require less binder. These two factors are balancedagainst each other for selecting the best average thickness for anyparticular application. The average thickness of the wood flakes 12preferably is about 0.015 to about 0.25 inches, and more preferablyabout 0.0020 inch.

The width of the wood flakes 12 is less important. The wood flakes 12should be wide enough to ensure that they lie substantially flat whenfelted during mat formation. The average width generally should be about3 inches or less and no greater than the average length. For bestresults, the majority of the wood flakes 12 should have a width of about{fraction (1/16)} inch to about 3 inches, and preferably 0.25 to 1.0inches.

The blade setting on a flaker can primarily control the thickness of thewood flakes 12. The length and width of the wood flakes 12 are alsocontrolled to a large degree by the flaking operation. For example, whenthe wood flakes 12 are being prepared by ring flaking fingerlings, thelength of the fingerlings generally sets the maximum lengths. Otherfactors, such as the moisture content of the wood and the amount of barkon the wood affect the amount of fines produced during flaking. Dry woodis more brittle and tends to produce more fines. Bark has a tendency tomore readily break down into fines during flaking and subsequenthandling than wood.

While the flake size can be controlled to a large degree during theflaking operation as described above, it usually is necessary to usesome sort of classification in order to remove undesired particles, bothundersized and oversized, and thereby ensure that the average length,thickness and width of the wood flakes 12 are within the desired ranges.When roundwood flaking is used, both screen and air classificationusually are required to adequately remove both the undersize andoversize particles, whereas fingerling wood flakes 12 usually can beproperly sized with only screen classification.

Wood flakes 12 from some green wood can contain up to 90% moisture. Themoisture content of the mat must be substantially less for molding asdiscussed below. Also, wet wood flakes 12 tend to stick together andcomplicate classification and handling prior to blending. Accordingly,the wood flakes 12 are preferably dried prior to classification in aconventional type drier, such as a tunnel drier, to the moisture contentdesired for the blending step. The moisture content to which the woodflakes 12 are dried usually is in the order of about 6 weight % or less,preferably about 2 to about 5 weight %, based on the dry weight of thewood flakes 12. If desired, the wood flakes 12 can be dried to amoisture content in the order of 10 to 25 weight % prior toclassification and then dried to the desired moisture content forblending after classification. This two-step drying may reduce theoverall energy requirements for drying wood flakes 12 prepared fromgreen woods in a manner producing substantial quantities of particleswhich must be removed during classification and, thus, need not be asthoroughly dried.

To coat the wood flakes 12 prior to being placed as a felted mat 52within the cavity 30 within the mold 10, a known amount of the dried,classified wood flakes 12 is introduced into a conventional blender,such as a paddle-type batch blender, wherein predetermined amounts of aresinous particle binder, and optionally a wax and other additives, isapplied to the wood flakes 12 as they are tumbled or agitated in theblender. Suitable binders include those used in the manufacture ofparticle board and similar pressed fibrous products and, thus, arereferred to herein as “resinous particle board binders.” Representativeexamples of suitable binders include thermosetting resins such asphenolformaldehyde, resorcinol-formaldehyde, melamine-formaldehyde,urea-formaldehyde, urea-furfuryl and condensed furfuryl alcohol resins,and organic polyisocyantes, either alone or combined with urea- ormelamine-formaldehyde resins.

Particularly suitable polyisocyanates are those containing at least twoactive isocyanate groups per molecule, including diphenylmethanediisocyanates, m- and p-phenylene diisocyanates, chlorophenylenediisocyanates, toluene di- and triisocyanates, triphenylmethenetriisocyanates, diphenylether-2,4,4′-triisoccyanate andpolyphenylpolyisocyanates, particularlydiphenylmethane4,4′-diisocyanate. So-called MDI is particularlypreferred.

The amount of binder added to the wood flakes 12 during the blendingstep depends primarily upon the specific binder used, size, moisturecontent and type of the wood flakes 12, and die desired characteristicsof the part being formed. Generally, the amount of binder added to thewood flakes 12 is about 2 to about 15 weight %, preferably about 4 toabout 10 weight %, as solids based on the dry weight of the wood flakes12. When a polyisocyanate is used alone or in combination with aurea-formaldehyde resin, the amounts can be more toward the lower endsof these ranges.

The binder can be admixed with the wood flakes 12 in either dry orliquid form. To maximize coverage of the wood flakes 12, the binderpreferably is applied by spraying droplets of the binder in liquid formonto the wood flakes 12 as they are being tumbled or agitated in theblender. When polyisocyantes are used), a conventional mold releaseagent preferably is applied to the die or to the surface of the feltedmat prior to pressing. To improve water resistance of the part, aconventional liquid wax emulsion preferably is also sprayed on the woodflakes 12 during the blinding step. The amount of wax added generally isabout 0.5 to about 2 weight %, as solids based on die dry weight of thewood flakes 12. Other additives, such as at least one of the following:a coloring agent, fire retardant, insecticide, fungicide, mixturesthereof and the like may also be added to the wood flakes 12 during theblending step. The binder, wax and other additives, can be addedseparately in any sequence or in combined form.

The moistened mixture of binder, wax and wood flakes 12 or “furnish”from the blending step is formed into a loosely-felled, layered mat 52,which is placed within the cavity 30 prior to the molding and curing ofthe felted mat 52 into molded wood flake part 14. The moisture contentof the wood flakes 12 should be controlled within certain limits so asto obtain adequate coating by the binder during the blending step and toenhance binder curing and deformation of the wood flakes 12 duringmolding.

The presence of moisture in the wood flakes 12 facilitates their bendingto make intimate contact with each other and enhances uniform heattransfer throughout the mat during the molding step, thereby ensuringuniform curing. However, excessive amounts of water tend to degrade somebinders, particularly urea-formaldehyde resins, and generate steam whichcan cause blisters. On the other hand, if the wood flakes 12 are toodry, they tend to absorb excessive amounts of the binder, leaving aninsufficient amount on the surface to obtain good bonding and thesurfaces tend to cause hardening which inhibits the desired chemicalreaction between the binder and cellulose in the wood. This lattercondition is particularly true for polyisocyanate binders.

Generally, the moisture content of the furnish after completion ofblending, including the original moisture content of the wood flakes 12and the moisture added during blending with the binder, wax and otheradditives, should be about 5 to about 25 weight %, preferably about 8 toabout 12 weight %. Generally, higher moisture contents within theseranges can be used for polyisocyanate binders because they do notproduce condensation products upon reacting with cellulose in the wood.

The furnish is formed into the generally flat, loosely-felted mat 52,preferably as multiple layers. A conventional dispensing system, similarto those disclosed in U.S. Pat. Nos. 3,391,223 and 3,824,058, and4,469,216 can be used to form the felted mat 52. Generally, such adispensing system includes trays, each having one open side, carried onan endless belt or conveyor and one or more (e.g., three) hoppers spacedabove and along the belt in the direction of travel for receiving thefurnish.

When a multi-layered felted mat 52 is formed, a plurality of hoppersusually are used with each having a dispensing or forming head extendingacross the width of the carriage for successively depositing a separatelayer of the furnish as the tray is moved beneath the forming heads.Following this, the tray is taken to the mold to place the felted matwithin the cavity of the bottom mold, by sliding the tray out from underthe mat.

In order to produce molded wood flake parts 14 having the desired edgedensity characteristics without excessive blistering and springback, thefelted mat should preferably have a substantially uniform thickness andthe wood flakes 12 should lie substantially flat in a horizontal planeparallel to the surface of the carriage and be randomly orientedrelative to each other in that plane. The uniformity of the matthickness can be controlled by depositing two or more layers of thefurnish on the carriage and metering the flow of furnish from theforming heads.

Spacing the forming heads above the carriage so the wood flakes 12 mustdrop about 1 to about 3 feet from the heads en route to the carriage canenhance the desired random orientation of the wood flakes 12. As theflat wood flakes 12 fall from that height, they tend to spiraldownwardly and land generally flat in a random pattern. Wider woodflakes 12 within the range discussed above enhance this action. Ascalper or similar device spaced above the carriage can be used toensure uniform thickness or depth of the mat, however, such meansusually tend to align the top layer of wood flakes 12, i.e., eliminatethe desired random orientation. Accordingly, the thickness of the matthat would optimally have the nominal part thickness 100 preferablycontrolled by closely metering the flow of furnish from the formingheads. The mat thickness that would optimally have the nominal partthickness 100 used will vary depending upon such factors as the size andshape of the wood flakes 12, the particular technique used for formingthe mat 52, the desired thickness and density of the molded wood flakepart 14 produced, the configuration of die molded wood flake part 14,and the molding pressure to be used. However, as discussed above, thefelted mats 52 will be compressed to varying thicknesses by the mold 10,due to unavoidable inconsistencies from mat 52 to mat 52, spring back ofthe mat 52, overcompression, or the like.

Following the production of the felted mat 52 and placement of thefelted mat 52 within the cavity 30 of the mold 10, the felted mat 52 matis compressed and cured under heat and pressure when the top mold die 16engages the bottom mold die 18. During this molding process, the punch22 attached to and projecting from the top mold die 16 pushes throughthe binder coated wood flakes 12 of the felted mat 52 and forms the hole24 while an end of the cylindrical lower portion 34 of the punch 22 isreceived by the punch receiving aperture 28 in the punch receivinginsert 58 of the bottom mold die 18.

The felted mat 52 is then compressed and cured between the top mold die16 and the bottom mold 18 to become the molded wood flake part 14. Afterthe molded wood flake part 14 is produced by the method of the presentinvention, any flashing and any plugs are removed by conventional meansto reveal the hole or holes 24, depending upon the number of punches 22used during the molding process. Such holes 24 are capable of receivinginsertion material, such as T nuts, in an assembly line fashion.

Thus, holes 24 can be produced for a multitude of inserts, such as Tnuts, having a variety of shapes and sizes, which could not have beendone previously. In addition, the placement of such inserts within themolded wood flake part 14 in an assembly-line fashion improvesproduction efficiency and reduces cost in producing such parts, whichcould not be done previously.

The above description is that of the preferred embodiments only.Modifications of the invention will occur to those skilled in the artand to those who make or use the invention. Therefore, it is understoodthat the embodiment described above is merely for illustrative purposesand not intended to limit the scope of the invention, which is definedby the following claims as interpreted according to the principles ofpatent law, including the Doctrine of Equivalents.

1. A mold for forming wood flakes into a molded wood flake partcomprising: a top mold die including a surface and a punch extendingfrom the surface for forming a hole in the part; and a bottom mold dieincluding a surface having a punch receiving aperture; said surface ofsaid top mold die and said surface of said bottom mold die defining acavity therebetween; said panch projecting, into said cavity from saidsurface of said top mold die, and including a tapered upper portion anda cylindrical lower portion for, forming the hole in molded parts ofvarying thickness, said punch including a tapered upper section definingan upper opening of a first radius in a top surface of the molded partand a cylindrical lower section defining an opening of a second radiusin a bottom surface of the molded part, said tapered upper portionconfigured to extend sufficiently far into the molded part to facilitatewithdrawal of said punch from the hole formed therein, and saidcylindrical lower portion being sufficiently long that regardless ofvariations in part thickness, the bottom opening in the hole in eachpart formed will have the same second radius, defined by said lowercylindrical portion.
 2. The mold as defined in claim 1, wherein: thelength of said tapered upper portion of said punch is approximatelyequal to the length of said cylindrical lower portion of said punch. 3.The mold as defined in claim 1, wherein: said punch receiving aperturehas a cross-sectional configuration having larger dimensions than across-sectional configuration of said punch such that said punch can beeasily inserted into said punch receiving aperture.
 4. The mold asdefined in claim 3, wherein: said punch receiving aperture includes atapered sidewall.
 5. A method of forming a molded wood flake part fromwood flakes comprising: providing a top mold die including a surface anda punch extending from the surface for forming holes in the wood flakes,said punch including a tapered upper portion and a cylindrical lowerportion for forming the hole in molded parts of varying thicknesses,said punch including a tapered upper section defining an upper openingof a first radius in a top surface of the molded part and a cylindricallower section defining an opening of a second radius in a bottom surfaceof the molded part, said tapered upper portion configured to extendsufficiently far into the molded part to facilitate withdrawal of saidpunch from the hole formed therein, and said cylindrical lower portionbeing sufficiently long that regardless of variations in part thickness,the bottom opening in the hole in each part formed will have the samesecond radius, defined by said lower cylindrical portion; providing abottom mold die, said surface of said top mold die and said surface ofsaid bottom mold die being configured to define a cavity therebetween;molding said wood flakes between said top mold die and said bottom molddie; and forming said hole in said molded wood flake part.
 6. The methodof forming a molded wood flake part from wood flakes as defined in claim5, further including: forming a loosely felted mat of said wood flakes;and depositing said mat onto said bottom mold die; wherein said step ofmolding includes compressing and heating said mat between said uppermold die and said bottom mold die.
 7. The method of forming, a moldedwood flake part from wood flakes as defined in claim 5, furtherincluding: providing said bottom mold die with a punch receivingaperture into which wood flakes are pressed by said punch.
 8. The methodof forming a molded wood flake part from wood flakes as defined in claim7, wherein: said punch receiving aperture has a cross-sectionalconfiguration having larger dimensions than a cross-sectionalconfiguration of said punch such that said punch can be easily insertedinto said punch receiving aperture.
 9. The method of forming a moldedwood flake part from wood flakes as defined in claim 8, wherein: saidpunch receiving aperture includes a tapered sidewall.
 10. The method offorming a molded wood flake part from wood flakes as defined in claim 5,wherein: the length of said tapered upper portion of said punch isapproximately equal to the length of said cylindrical lower portion ofsaid punch.
 11. The method of forming a molded wood flake part from woodflakes is defined in claim 5, wherein: said wood flakes have an averagelength of from about 1¼ to about 6 inches, an average thickness of fromabout 0.015 to about 0.25 inches, and an average width of less than theaverage length an no greater than about 3 inches.